10 most difficult at­mos­phere riddles

Auroras are produced when the magnetosphere is sufficiently disturbed by the solar wind that the trajectories of charged particles in both solar wind and magnetospheric plasma, mainly in the form of electrons and protons, precipitate them into the upper atmosphere (thermosphere/exosphere) due to Earth's magnetic field, where their energy is lost.

Argon makes up 0.934% of the earth's atmosphere. It is more than twice as abundant as water vapor and 23 times as abundant as carbon dioxide.

Halo is the name for a family of optical phenomena produced by light interacting with ice crystals suspended in the atmosphere. Halos can have many forms, ranging from colored or white rings to arcs and spots in the sky. Among the best known halo types are the circular halo (properly called the 22° halo), Other common optical phenomena involving water droplets rather than ice crystals include the glory and the rainbow.

Cirrostratus is a high-level, very thin, generally uniform stratiform genus-type of cloud, composed of ice-crystals.

Arcus clouds most frequently form along the leading edge or "gust fronts" of thunderstorm outflow; some of the most dramatic arcus formations mark the gust fronts of derecho-producing convective systems. Roll clouds also may arise in the absence of thunderstorms, forming along the shallow cold air currents of some sea breeze boundaries and cold fronts.

St. Elmo's fire is a form of plasma. The electric field around the object in question causes ionization of the air molecules, producing a faint glow easily visible in low-light conditions. Conditions that can generate St. Elmo's fire are present during thunderstorms, when high voltage differentials are present between clouds and the ground underneath. The nitrogen and oxygen in the Earth's atmosphere cause St. Elmo's fire to fluoresce with blue or violet light; this is similar to the mechanism that causes neon lights to glow

Catatumbo lightning is an atmospheric phenomenon in Venezuela. It occurs only over the mouth of the Catatumbo River where it empties into Lake Maracaibo. The phenomenon is characterized by almost continuous lightning and occurs during 260 nights a year, 10 hours per day and up to 280 times per hour. It has been known for centuries as the Lighthouse of Maracaibo, since it is visible for miles around Lake Maracaibo

The effect is similar to irisation. Iridescent clouds are a diffraction phenomenon caused by small water droplets or small ice crystals individually scattering light. Larger ice crystals do not produce iridescence, but can cause halos, a different phenomenon.

Noctilucent clouds, or night shining clouds, are tenuous cloud-like phenomena in the upper atmosphere of Earth. They are first known to have been observed in 1885, two years after the eruption of Krakatoa volcano. Noctilucent clouds require water vapour, dust and exhaust. The dust is believed to come from micrometeors, although particulates from volcanoes and dust from the troposphere are also possibilities. The exhaust are from Space Shuttles.

In the ozone layer, ozone molecules absorb UV-B and UV-C radiation - short wavelength forms of ultraviolet that can disrupt organic molecules, producing cancerous changes in living cells.